Method of producing compound originating from polysaccharide-based bio-mass

ABSTRACT

A method of producing a compound originating from a polysaccharide-based biomass includes at least one of a saccharification step that produces a sugar solution containing a monosaccharide and/or an oligosaccharide from a product obtainable by hydrolyzing the polysaccharide-based biomass; a fermentation step that ferments the sugar solution containing the monosaccharide and/or oligosaccharide originating from the polysaccharide-based biomass; and a treatment that removes a fermentation inhibitor with the use of a separation membrane having a glucose removal rate and an isopropyl alcohol removal rate which simultaneously satisfy the following relationships (I) and (II) when a 500 ppm aqueous glucose solution at pH 6.5 at 25° C. and a 500 ppm aqueous isopropyl alcohol solution at pH 6.5 at 25° C. are respectively permeated through the membrane at an operation pressure of 0.5 MPa, prior to the saccharification step and/or in the step prior to the fermentation step:
 
Glucose removal rate≧80%  (I)
 
Glucose removal rate−Isopropyl alcohol removal rate≧20%  (II).

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.12/920,128, filed on Aug. 30, 2010, now issued as U.S. Pat. No.8,497,091, which is a 371 of PCT/JP2009/053629 filed Feb. 27, 2009,which claims priority to Japanese Application No. 2008-054472 filed Mar.5, 2008.

TECHNICAL FIELD

This disclosure relates to a highly efficient method of producing acompound originating from a polysaccharide-based biomass, the methodincluding providing a treatment for removing a fermentation inhibitorwith the use of a separation membrane in the step prior to thesaccharification step and/or in the step prior to the fermentation step,in at least one of the following steps, that is, a step for producing amonosaccharide and/or an oligosaccharide of a pentose and/or a hexose byusing a polysaccharide-based biomass as a starting material, and a stepfor converting the monosaccharide and/or oligosaccharide thus obtainedinto a chemical via fermentation.

BACKGROUND

The twentieth century, which is known as the era of mass consumption andmass disposal, has come to an end, and in the twenty-first century whereestablishment of an environmentally friendly society is demanded, as theproblem of depletion of fossil resources and the problem of globalwarming are becoming more serious, promotion of the utilization ofbiomass resources, which are recyclable resources, is under expectation.

Currently, among the biomass resources, production of bioethanol usingsugar cane or corn as a starting material is in active progress in theUnited States, Brazil and the like. This is because sugar cane or corncontains a rich content of sucrose or starch, and accordingly, it iseasy to prepare a sugar solution therefrom for fermentation. However,sugar cane and corn are originally foodstuffs, and when these are usedas starting materials, there is a serious problem that a competitionoccurs between the usage as the starting material and the usage asfoodstuffs or feedstock, causing an increase in the starting materialprice. Thus, development of a technology to use a non-edible biomass asa starting material is under way.

Examples of the non-edible biomass include cellulose that is presentmost abundantly on Earth, and most of cellulose exists in the form of apolysaccharide-based biomass which is a complex of cellulose with ligninor a hemicellulose, which is an aromatic polymer. A technology ofproducing a monosaccharide or an oligosaccharide of a pentose or ahexose from cellulose or hemicelluloses in a polysaccharide-basedbiomass, fermenting the obtained monosaccharide or oligosaccharide, andconverting the fermentation product to various compounds originatingfrom a polysaccharide-based biomass, such as ethanol or lactic acid, isattracting public attention. However, as described in TechnologiesUtilizing Biomass Energy, reviewed by Yukawa, Hideaki, CMC Publishing,Inc, (2006), a polysaccharide-based biomass is a complicated constructof cellulose, hemicelluloses and lignin, and cellulose or hemicellulosesare protected by lignin from being subjected to biodegradation, so thatthe composition ratios vary in a wide range depending on the regionaland seasonal conditions and the starting material. For this reason, itis not easy to selectively pick out only a monosaccharide or anoligosaccharide of a pentose or a hexose.

Investigations have hitherto been made on a pretreatment method ofdestroying or softening the protective walls of lignin by treating apolysaccharide-based biomass using an acid, an alkali, an enzyme,subcritical water (supercritical water) or the like, and recovering aliquid or solid containing a monosaccharide or an oligosaccharide of apentose or a hexose. For example, since a treatment based on subcriticalwater (supercritical water) has a short treatment time, and does notrequire a mineral acid or the like, that is, does not require aneutralization treatment, the treatment is advantageous from anenvironmental aspect such that a side product such as plaster is notgenerated. Thus, this treatment is attracting attention as anext-generation treatment method of environmentally conscious type.However, as described in JP-A-2005-270056, since subcritical water(supercritical water) is highly reactive, there are difficulties incontrolling the reactivity, and various fermentation inhibitors such asfurfural and 5-hydroxymethylfurfural, which are overdegradation productsof sugars, as well as vanillin and guaiacol, which are lignin-derivedaromatic compounds, are also generated at the same time, so that thetreatment product cannot be directly used in the fermentation step.Furthermore, according to the pretreatment conditions, the concentrationof the obtainable monosaccharide or oligosaccharide of a pentose or ahexose may be low, and in this case, it is necessary to carry out simpleconcentration of the monosaccharide or oligosaccharide to aboutseveral-fold to ten-fold before supplying the monosaccharide oroligosaccharide to the fermentation process. At this time, while themonosaccharide or oligosaccharide of a pentose or a hexose isconcentrated, the fermentation inhibitors are also concentrated at thesame time, so that it is difficult to use the concentrate in thefermentation process.

In regard to such problems, investigations are being made on the removalof fermentation inhibitors. For instance, Biotechnology Letters, Vol. 5,No, 3, pp. 175-178 (1983) discloses a method of removing a fermentationinhibitor through adsorption to activated carbon. However, this methodhas a problem that since the activated carbon adsorbs not onlyfermentation inhibitors but also monosaccharides or oligosaccharides ofpentoses or hexoses, the yield of the monosaccharides oroligosaccharides of pentoses or hexoses is decreased.

JP-A-2005-270056 discloses a method of removing fermentation inhibitorsthrough adsorption to wood-based carbon, and in this method, sincefermentation inhibitors can be selectively adsorbed and removed, amonosaccharide or an oligosaccharide of a pentose or a hexose can beobtained with a good yield. However, since the removal mechanisminvolves adsorption, if the adsorption capacity is saturated, thefermentation inhibitors run off and contaminate the apparatuses, pipesand the like in the subsequent steps. Unless the fermentation reactionis carried out accurately, high quality products cannot be obtained, andespecially in the case of carrying out the production by continuouslyoperating the apparatuses while continuously supplying the startingmaterials, a method of stably and certainly removing fermentationinhibitors is desired, because the occurrence of contamination ofapparatuses, pipes and the like brings on an increase in the cost and adecrease in the product quality. Furthermore, in the case of using astarting material having a low concentration of a monosaccharide oroligosaccharide of a pentose or a hexose, a method capable of reducingtwo steps, namely, a step for the concentration of a monosaccharide oran oligosaccharide of a pentose or a hexose and a step for the removalof fermentation inhibitors, into one step, or reducing the burden of theconcentration step, is desired from the viewpoint of reducing the costand enhancing the product quality.

On the other hand, in the case of using construction waste materialssuch as plywood as a polysaccharide-based biomass, acetic acid, formicacid and the like originating from the adhesive contained in the plywoodact as fermentation inhibitors. There, JP-A-2004-187650 discloses amethod of removing volatile fermentation inhibitors such as acetic acidand formic acid by distillation. This method is barely effective onlywhen the non-volatile fermentation inhibitors that cannot be removed bydistillation are present at a concentration that does not have adverseeffects on the fermentation process, and it is difficult to apply themethod when a polysaccharide-based biomass having a broad compositionrange is used as a starting material.

It could therefore be helpful to provide a method of producing acompound originating from a polysaccharide biomass by stably andcertainly removing fermentation inhibitors that serve as an obstacle toreduce the burden of and to promote streamlining of at least one of thefollowing steps, that is, a step for producing a monosaccharide and/oran oligosaccharide of a pentose and/or a hexose using apolysaccharide-based biomass having a broad composition range as astarting material, and a step for converting the monosaccharide and/oroligosaccharide thus obtained into a chemical via fermentation.

SUMMARY

We thus provide:

-   -   1) A method of producing a compound originating from a        polysaccharide-based biomass, the method including at least one        of a saccharification step for producing a sugar solution        containing a monosaccharide and/or an oligosaccharide from a        product obtainable by hydrolyzing the polysaccharide-based        biomass, and a fermentation step for fermenting the sugar        solution containing the monosaccharide and/or oligosaccharide        originating from the polysaccharide-based biomass, wherein a        treatment for removing a fermentation inhibitor with the use of        a separation membrane having a glucose removal rate and an        isopropyl alcohol removal rate which simultaneously satisfy the        following relationships (I) and (II) when a 500 ppm aqueous        glucose solution at pH 6.5 at 25° C. and a 500 ppm aqueous        isopropyl alcohol solution at pH 6.5 at 25° C. are respectively        permeated through the membrane at an operation pressure of 0.5        MPa, is carried out in the step prior to the saccharification        step and/or in the step prior to the fermentation step:        Glucose removal rate≧80%  (I)        Glucose removal rate−Isopropyl alcohol removal rate≧20%  (II).    -   2) The method of producing a compound originating from a        polysaccharide-based biomass as set forth in item 1), wherein        the treatment for removing a fermentation inhibitor with the use        of a separation membrane allows removal of the fermentation        inhibitor and concurrent concentration of cellulose, a        hemicellulose, a monosaccharide and/or an oligosaccharide.    -   3) The method of producing a compound originating from a        polysaccharide-based biomass as set forth in item 1), wherein a        treatment for concentrating the compound with the use of a        reverse osmosis membrane is performed after the treatment for        removing a fermentation inhibitor with the use of a separation        membrane, and before the fermentation step.    -   4) The method of producing a compound originating from a        polysaccharide-based biomass as set forth in item 1), wherein        the treatment for removing a fermentation inhibitor with the use        of a separation membrane is carried out until the content of the        fermentation inhibitor in the sugar solution obtainable        immediately before the fermentation step reaches 500 ppm or        less.    -   5) The method of producing a compound originating from a        polysaccharide-based biomass as set forth in item 1), wherein        the separation membrane has pores having an average pore radius        as measured by a positron annihilation lifetime spectroscopy, of        from 0.8 nm to 4.0 nm.    -   6) The method of producing a compound originating from a        polysaccharide-based biomass as set forth in item 5), wherein        the average pore radius is from 2.5 nm to 4.0 nm.

There is provided a method of producing a compound originating from apolysaccharide biomass, in which method a treatment for removing, withthe use of a separation membrane, a fermentation inhibitor which servesas an obstacle in at least one of the following steps, that is, a stepfor producing a monosaccharide and/or an oligosaccharide of a pentoseand/or a hexose using a polysaccharide-based biomass as a startingmaterial, and a step for converting the monosaccharide and/oroligosaccharide thus obtained into a chemical via fermentation, isperformed in the step prior to the saccharification step and/or in thestep prior to the fermentation step. The separation membrane is capableof continuously removing fermentation inhibitors and is capable ofcontrolling the water quality when separation membranes are selected andconnected as necessary. Furthermore, the method of supplying raw waterto the separation membrane can also be freely designed, such as toinclude varying the recovery rate or circulating a part of the rawwater. Therefore, it is made possible to remove fermentation inhibitorsto a concentration that does not adversely affect the subsequentprocesses, even when a polysaccharide-based biomass having a broadcomposition range is used as a starting material.

DETAILED DESCRIPTION

The polysaccharide-based biomass that is a subject to be treated by themethod mainly contains cellulose, hemicellulose and lignin, and examplesthereof include agroforestry resources, agroforestry waste materials andagroforestry processed products such as softwood, hardwood, constructionwaste materials, forest wood residues, pruned wood waste, rice straw,rice husk, wheat straw, wood chip, wood fiber, chemical pulps, usedpaper and plywood. In addition, materials containing less or no lignin,for example, sucrose-containing resources such as sugar cane and sugarbeet, and starch-containing resources such as corn and sweet potato, mayalso be used as the subject to be treated by the method as long as thematerials contain or produce fermentation inhibitors, representativeexamples of which include overdegradation products of sugars. Thesepolysaccharide-based biomasses may be used singly or may be used in amixture.

Hemicelluloses have sugars called pentoses such as xylose, each havingfive carbon atoms as constituent units, sugars called hexoses such asmannose, arabinose and galacturonic acid, each having six carbon atomsas constituent units, and complex polysaccharides such as glucomannanand glucuronoxylan. Thus, when subjected to hydrolysis, hemicellulosesgenerate a monosaccharide of a pentose formed from five carbon atoms, anoligosaccharide of a pentose having a plural number of themonosaccharide linked together, a monosaccharide of a hexose formed fromsix carbon atoms, an oligosaccharide of the hexose having a pluralnumber of the monosaccharide connected together, and an oligosaccharidehaving plural numbers of a monosaccharide of a pentose and amonosaccharide of a hexose linked together. Cellulose has six carbonatoms as constituent units, and thus when subjected to hydrolysis,cellulose generates a monosaccharide of a hexose formed from six carbonatoms, and an oligosaccharide of the hexose having a plural number ofthe monosaccharide linked together. In general, the composition ratio orthe production amount of a monosaccharide and/or an oligosaccharide of apentose and/or a hexose varies with the pretreatment method or the typeof the agroforestry resource, agroforestry waste material oragroforestry processed product used as a starting material.

Various treatment flows for polysaccharide-based biomasses have beensuggested, but the outline can be explained as follows. First, apolysaccharide-based biomass is treated by hydrolysis to remove orsoften lignin, and is supplied to a pretreatment process for makingextraction of cellulose or a hemicellulose easy. Subsequently, asaccharification process is carried out in which the cellulose and ahemicellulose thus obtained are further treated by hydrolysis, and amonosaccharide and/or an oligosaccharide of a pentose and/or a hexose iscollected. The hydrolysis treatments in the pretreatment process and thesaccharification process may be, for example, treatments making use ofacid, alkali, enzyme, high temperature and high pressure (subcriticalwater, supercritical water) or the like, and these treatments can beused singly or in combination.

Furthermore, the pretreatment process and the saccharification processmay be carried out each independently, or may be carried outconcurrently. After the saccharification process, a fermentation processis carried out in which cellulose, a hemicellulose, a monosaccharideand/or an oligosaccharide of a pentose and/or a hexose are used asstarting materials to convert them via fermentation into variouscompounds originating from a polysaccharide-based biomass, such asalcohols such as ethanol, butanol, 1,3-propanediol, 1,4-butanediol andglycerol; organic acids such as pyruvic acid, succinic acid, malic acid,itaconic acid, citric acid and lactic acid; nucleosides such as inosineand guanosine; nucleotides such as inosinic acid and guanylic acid; anddiamine compounds such as cadaverine. When the compound thus obtainedvia fermentation is a monomer such as lactic acid, a polymerizationprocess for converting the monomer into a polymer via polymerization mayalso be carried out. Finally, after the fermentation process or thepolymerization process, a purification process is often carried out soas to enhance the quality of the resulting various compounds originatingfrom a polysaccharide-based biomass.

As described above, in the pretreatment process or saccharificationprocess, the polysaccharide-based biomass is subjected to a hydrolysistreatment according to a known method making use of acid, alkali,enzyme, high temperature and high pressure (subcritical water,super-critical water), or the like. The type or conditions of thehydrolysis treatment may be appropriately selected in view of the typeof the polysaccharide-based biomass used as the starting material, andthe cost for the overall process including fermentation, polymerization,purification and the like. The hydrolysis treatment may be carried outas single hydrolysis treatment, or may be carried out in combination ofmultiple hydrolysis treatments. For example, if an acid is used in thehydrolysis treatment in any of the pretreatment process and thesaccharification process, the pretreatment process and thesaccharification process may be carried out in the same step, or therespective processes may be carried out independently such that thepretreatment process is carried out under a relatively highertemperature, while the saccharification process is carried out at arelatively lower temperature. There may also be employed, for example, amethod of carrying out a pretreatment process which is focused on theremoval or softening of lignin with the use of subcritical water, andthen subsequently carrying out a saccharification process which isfocused on the production of a monosaccharide and/or an oligosaccharideof a pentose and/or a hexose from cellulose or a hemicellulose with theuse of an enzyme.

From the polysaccharide-based biomass which has been subjected to ahydrolysis treatment in the pretreatment process, various side productsare obtained in addition to the monosaccharide and/or oligosaccharide ofa pentose and/or a hexose. If those side products are substances that donot adversely affect the enzymatic saccharification, fermentation andthe like of the subsequent steps, the side products may be removed inany process such as a purification process for enhancing the productquality, and thus do not raise a serious problem. However, if the sideproducts are fermentation inhibitors that have adverse effects, therearises a necessity to remove the side products in the steps prior to theenzymatic saccharification and fermentation, to an extent that the sideproducts do not adversely affect the respective processes.

In general, a fermentation inhibitor is a substance that obstructs anenzymatic reaction or a fermentation reaction in a saccharificationprocess making use of enzyme or in a fermentation process.Representative examples of the fermentation inhibitor includeoverdegradation products of sugars, lignin or lignin-derived aromaticcompounds, and compounds originating from adhesives or coatingmaterials. Among these, those compounds originating from artificialchemicals such as adhesives and coating materials can be avoided to someextent, by using naturally occurring polysaccharide-based biomasses thathave not be subjected to those treatments. However, as long as apolysaccharide-based biomass is used as a starting material, it isdifficult to avoid the generation of overdegradation products of sugarsor lignin-derived aromatic compounds. When the fermentation inhibitorsare insoluble solids such as lignin, and cellulose, hemicelluloses,monosaccharides and/or oligosaccharides of pentoses and/or hexoses aresoluble, it may be possible to remove the fermentation inhibitors viaconventional solid-liquid separation. However, if the fermentationinhibitors as well as the useful substances are all soluble,conventional solid-liquid separation cannot be applied, and therefore,the treatment method of removing a fermentation inhibitor with the useof a separation membrane as used in the present invention is appliedwith preference. That is, a fermentation inhibitor refers to a materialwhich substantially forms a mixed solution with cellulose, ahemicellulose, a monosaccharide and/or an oligosaccharide of a pentoseof a hexose, and is in a state of being inseparable or hardly separablethrough conventional solid-liquid separation. Examples of such afermentation inhibitor include acetic acid, formic acid, levulinic acid,furfural and 5-hydroxymethylfurfural, which are overdegradation productsof sugars, vanillin, acetovanillin and guaiacol, which arelignin-derived aromatic compounds.

The fermentation inhibitor concentration that inhibits an enzymaticreaction or a fermentation reaction may vary with the respectivereactions, but is generally said to be a concentration of 500 to 1000ppm or greater. Accordingly, it is preferable to remove the fermentationinhibitor to a concentration of 500 ppm or less, more preferable toremove to a concentration of 150 ppm or less, and most preferable toremove to 0 ppm (detection limit), before the fermentation inhibitor issupplied to a saccharification process making use of enzyme or afermentation process. As the fermentation inhibitor concentration isremoved more and more, the burden of the saccharification process makinguse of enzyme or the fermentation process is reduced, and thus moreefficient operation of the saccharification process making use of enzymeor the fermentation process can be attempted. However, in practice, thecost required in the step for removing the fermentation inhibitor withthe use of a separation membrane and the cost required in the processesfor enzymatic saccharification, fermentation, polymerization,purification and the like in the subsequent steps are taken intoconsideration, and the fermentation inhibitor concentration that wouldgive a minimum total cost is calculated.

A separation membrane is used to remove a fermentation inhibitor from asolution containing cellulose, a hemicellulose, a monosaccharide and/oran oligosaccharide of a pentose and/or a hexose, and the separationmembrane is not particularly limited as long as it is capable ofseparating the fermentation inhibitor from cellulose, a hemicellulose, amonosaccharide and/or an oligosaccharide of a pentose and/or a hexose.The fermentation inhibitor that is to be removed may vary with themethod of fermentation, but fermentation inhibitors are primarily lowmolecular weight compounds having a molecular weight of about 100 to200, such as overdegradation products of sugars or lignin-derivedaromatic compounds. On the other hand, the molecular weight of celluloseor a hemicellulose is generally as large as several hundreds to severalten thousands, while the molecular weight of a monosaccharide of apentose and/or a hexose is about 100 to 200. For this reason, it wasexpected that it would be difficult in particular to separate between afermentation inhibitor having a molecular weight of about 100 to 200 anda monosaccharide of a pentose and/or a hexose, on the basis of themembrane pore diameter, and the separation efficiency would be low.

However, we found that when a nanofiltration membrane is used as aseparation membrane, particularly the glucose removal rate is high, andon the other hand, when a nanofiltration membrane having a largedifference between the glucose removal rate and the isopropyl alcoholremoval rate is used, separation of the two substances is achieved withhigh efficiency.

A nanofiltration membrane is a material called nanofiltration(nanofiltration membrane, NF membrane), and is a membrane which isgenerally defined as “a membrane allowing permeation of a monovalent ionand blocking a divalent ion.” This is a membrane which is believed tohave micropores having a size of about a few nanometers, and is mainlyused for blocking microparticles, molecules, ions, salts and the like inwater.

The mechanism for separation of a solute with the use of ananofiltration membrane has not been satisfactorily elucidated even tothe present, but it is said that separation is achieved by a combinationof a separation mechanism based on charge repulsion, a separationmechanism based on the difference in the affinity to the separationmembrane, a separation mechanism based on the membrane pore diameter,and the like. It is not very difficult to imagine that a separationmembrane having a high removal rate for glucose, which is a kind of ahexose monosaccharide, would be able to concentrate a pentose or ahexose without permeating the sugar. However, it is a surprising factthat the tendency of separation between a fermentation inhibitor and themonosaccharides of a pentose and/or a hexose can be predicted by knowingthe difference between the removal rates for glucose and isopropylalcohol, which are non-chargeable organic substances. The reason is asfollows. Fermentation inhibitors contain a lot of compounds havingaromaticity, whether they be overdegradation products of sugars orlignin-derived aromatic compounds. In the separation between suchcompounds having aromaticity and those compounds that do not havearomaticity, such as pentoses or hexoses, the separation mechanism basedon the difference in the affinity to the separation membrane worksstrongly. Therefore, it has been thought to be difficult to predict thatthose compounds can be easily separated, only by investigating theseparation tendency of non-chargeable organic substances.

Although the reason of showing such a surprising tendency is notcertainly known, it is believed that the separation mechanism based onthe membrane pore diameter is predominant in the separation between themonosaccharides of pentoses and/or hexoses and the fermentationinhibitor with the use of a nanofiltration membrane of the separationmembrane used. That is, it is thought that since a monosaccharide of apentose and/or a hexose is highly hydrophilic, the monosaccharidemolecules many water molecules along with themselves in water and have alarge hydration radius. However, since a fermentation inhibitor has lowhydrophilicity, the inhibitor molecules does not a hydration radiussimilar to that of a monosaccharide of a pentose and/or a hexose, andthis difference in hydration radius has effects on the separationmechanism based on the membrane pore size, thereby separation beingachieved.

It is preferable to use a nanofiltration membrane as a separationmembrane. As the material for the nanofiltration membrane used, apolymeric material such as a cellulose ester-based polymer such ascellulose acetate, polyamide, polyester, polyimide or a vinyl polymercan be used. However, the membrane is not limited to a membraneconstructed from a single kind of material, and may also be a membranecontaining plural membrane materials. The membrane structure may beeither an asymmetric membrane which has a dense layer on at least onesurface of the membrane and has pores having a pore diameter thatgradually increases from the dense layer toward the interior of themembrane or toward the other surface, or a composite membrane having, onthe dense layer of the asymmetric membrane, a very thin functional layerformed from a different material. As the composite membrane, use can bemade of, for example, a composite membrane that constitutes a nanofilterformed from a polyamide functional layer on a supporting film ofpolysulfone as the film material, as described in JP-A-62-201606.

Among these, a composite membrane having a functional layer formed frompolyamide, which has high pressure resistance, high water permeabilityand high solute removal performance altogether and has an excellentpotential, is preferred. For the composite membrane to be able tomaintain durability against the operation pressure, high waterpermeability and blocking performance, a structure having a functionallayer made of polyamide and retaining the functional layer on a supportformed from a porous membrane or a non-woven cloth, is suitable.Furthermore, a suitable polyamide semipermeable membrane is a compositesemipermeable membrane having a crosslinked polyamide functional layerwhich is obtainable by a polycondensation reaction between apolyfunctional amine and a polyfunctional acid halide, provided on asupport.

In regard to a nanofiltration membrane having a functional layer made ofpolyamide, preferred examples of the carboxylic acid component of themonomer that constitutes the polyamide include aromatic carboxylic acidssuch as trimesic acid, benzophenonetetracarboxylic acid, trimelliticacid, pyrometic acid, isophthalic acid, terephthalic acid,naphthalenedicarboxylic acid, diphenylcarboxylic acid andpyridinecarboxylic acid. Upon the formation of a membrane, halides oranhydrides of these carboxylic acids are used with preference toincrease the reactivity with the amine component that will be describedbelow. However, if handlability such as solubility in solvent inparticular is taken into consideration, halides of trimesic acid,isophthalic acid, terephthalic acid and mixtures of these acids are morepreferred.

Preferred examples of the amine component for the monomer thatconstitutes the polyamide include primary diamines having aromaticrings, such as m-phenylenediamine, p-phenylenediamine, benzidine,methylenebisdianiline, 4,4′-diaminobiphenyl ether, dianisidine,3,3′,4-triaminobiphenyl ether, 3,3′,4,4′-tetraminobiphenyl ether,3,3′-dioxybenzidine, 1,8-naphthalenediamine,m(p)-monomethylphenylenediamine,3,3′-monomethylamino-4,4′-diaminobiphenyl ether,4,N,N′-(4-aminobenzoyl)-p(m)-phenylenediamine-2,2′-bis(4-aminophenylbenzoimidazole),2,2′-bis(4-aminophenylbenzoxazole) and2,2′-bis(4-aminophenylbenzothiazole); and secondary diamines such aspiperazine, 2,5-dimethylpiperazine, piperidine and derivatives thereof.A nanofiltration membrane having a functional layer made of acrosslinked polyamide containing piperazine or piperidine as a monomer,has heat resistance and chemical resistance in addition to pressureresistance and durability, and thus is used with preference. A morepreferred example is a polyamide containing the crosslinked piperazinepolyamide the crosslinked piperidine polyamide as a main component, anda more preferred example is a polyamide containing the crosslinkedpiperazine polyamide as a main component. Examples of the nanofiltrationmembrane containing a crosslinked piperazine polyamide as a maincomponent include those described in JP-A-62-201606, and a specificexample may be a crosslinked polyamide nanofiltration (NF) membrane(UTC-60) manufactured by Toray Industries, Inc.

Furthermore, even in the method of forming an ultrathin film layer of acrosslinked polyamide on a supporting film containing polysulfone as afilm material, and then treating the ultrathin film layer with anaqueous solution of a peroxymono compound or an aqueous solution of aperoxydisulfuric acid compound, as described in JP-A-5-96140, ananofiltration membrane is obtainable by controlling the treatmentconditions. The crosslinked polyamide can be produced from thecarboxylic acid components and amine components mentioned above.

A nanofiltration membrane is also obtainable by bringing a polyamidefilm having a functional layer that contains a primary amino group, intocontact under appropriate conditions, with a reagent that is capable ofproducing a diazonium salt or a derivative thereof by reacting with aprimary amino group, as described in JP-A-2005-177741. To obtain afunctional layer containing a primary amino group, among the aminecomponents mentioned above, a primary diamine having an aromatic ring,such as m-phenylenediamine, p-phenylenediamine, benzidine,methylenebisdianiline, 4,4′-diaminobiphenyl ether, dianisidine,3,3′,4-triaminobiphenyl ether, 3,3′,4,4′-tetraminobiphenyl ether,3,3′-dioxybenzidine, 1,8-naphthalenediamine,m(p)-monomethylphenylenediamine,3,3′-monomethylamino-4,4′-diaminobiphenyl ether,4,N,N′-(4-amino-benzoyl)-p(m)-phenylenediamine-2,2′-bis(4-aminophenylbenzoimidazole),2,2′-bis(4-aminophenylbenzoxazole), or2,2′-bis(4-aminophenylbenzothiazole), may be used.

As a nanofiltration membrane that is preferable as the separationmembrane, in particular, a nanofiltration membrane having a high glucoseremoval rate and having a large difference in the glucose removal rateand the isopropyl alcohol removal rate is preferred, because it iseasier to separate between a monosaccharide of a pentose and/or a hexoseand a fermentation inhibitor. Therefore, a nanofiltration membranehaving a glucose removal rate of 80% or greater and a difference betweenthe glucose removal rate and the isopropyl alcohol removal rate of 20%or greater is needed. It is more preferable that the glucose removalrate be 90% or greater, and it is even more preferable that the glucoseremoval rate be 95% or greater. Furthermore, it is more preferable thatthe difference between the glucose removal rate and the isopropylalcohol removal rate be 30% or greater, and it is even more preferablethat the glucose removal rate and the isopropyl alcohol removal rate be50% or greater.

A nanofiltration membrane having a glucose removal rate of 80% orgreater and a difference between the glucose removal rate and theisopropyl alcohol removal rate of 20% or greater is needed, but ananofiltration membrane can be appropriately selected so that, afterthese conditions are satisfied, a recovery rate for cellulose, ahemicellulose, a monosaccharide and/or an oligosaccharide of a pentoseand/or a hexose, and a recovery rate for a fermentation inhibitor may beobtained in view of the water quality of the liquid to be treated andthe total costs. For example, when the concentration of the fermentationinhibitor is low and the concentration of the cellulose, hemicellulose,monosaccharide and/or oligosaccharide of a pentose and/or a hexose ishigh, it is preferable to give priority to the glucose removal rate overthe difference between the glucose removal rate and the isopropylalcohol removal rate, so that the outflow of the cellulose,hemicellulose, monosaccharide and/or oligosaccharide of a pentose and/ora hexose can be suppressed, and then the fermentation inhibitor can beremoved. In this case, a glucose removal rate of the nanofiltrationmembrane of 95% or greater is preferred, a glucose removal rate of 98%or greater is more preferred, and a glucose removal rate of 99% orgreater is even more preferred. On the other hand, a difference betweenthe glucose removal rate and the isopropyl alcohol removal rate of thenanofiltration membrane of 25% or greater is preferred, and a differencebetween the glucose removal rate and the isopropyl alcohol removal rateof 30% or greater is more preferred. Furthermore, for example, when theconcentration of the fermentation inhibitor is high and theconcentration of the cellulose, hemicellulose, monosaccharide and/oroligosaccharide of a pentose and/or a hexose is low, it is preferable togive priority to the difference between the glucose removal rate and theisopropyl alcohol removal rate over the glucose removal rate, becausethe fermentation inhibitor can be removed in a short time. In this case,a difference between the glucose removal rate and the isopropyl alcoholremoval rate of the nanofiltration membrane of 30% or greater ispreferred, a difference between the glucose removal rate and theisopropyl alcohol removal rate of 50% or greater is more preferred, anda difference between the glucose removal rate and the isopropyl alcoholremoval rate of 60% or greater is even more preferred. On the otherhand, a glucose removal rate of the nanofiltration membrane of 90% orgreater is preferred, and a glucose removal rate of 95% or greater ismore preferred.

The glucose removal rate or the isopropyl alcohol removal rate isevaluated by using a 500 ppm aqueous glucose solution or a 500 ppmaqueous isopropyl alcohol solution at pH 6.5 at 25° C., permeating eachof the solutions through a separation membrane at an operation pressureof 0.5 MPa, and comparing the concentrations of glucose or isopropylalcohol in the permeation water and the source water. That is,calculation is performed by the following formula: glucose removal rate(%)=100×(1−(glucose concentration in permeation water/glucoseconcentration in source water)), and isopropyl alcohol removal rate(%)=100×(1−(isopropyl alcohol concentration in permeationwater/isopropyl alcohol concentration in source water)).

For the nanofiltration membrane showing a glucose removal rate and anisopropyl alcohol removal rate in the range mentioned above, when theaverage pore radius of the separation functional layer of the membraneis measured by a positron annihilation lifetime spectroscopy, it wasfound that the average pore radius is from 0.8 nm to 4.0 nm. Theseparation functional layer of the nanofiltration membrane is a layerresponsible for substantial separation of a solute in the nanofiltrationmembrane, and is generally located at the outermost layer or near thesurface layer of the nanofiltration membrane.

The positron annihilation lifetime spectroscopy is a technique ofmeasuring the time taken by a positron from the point of entrance into asample to the point of annihilation (in the order of several hundredpicoseconds to several ten nanoseconds), and non-invasively evaluatingthe data related to the size of pores of about 0.1 to 10 nm, the numberdensity and the size distribution based on the annihilation lifetime. Inregard to such an analysis method, the details are described in, forexample, “Lectures on Experimental Chemistry, 4^(th) Edition,” Vol. 14,p. 485, edited by the Chemical Society of Japan, published by MaruzenCorp. (1992).

This technique is roughly classified into two types based on the type ofthe positron radiation source. One type is a ²²Na method making use of aradioisotope (²²Na) as the positron radiation source, and is appropriatefor an evaluation of pores in resins, powders, fibers, liquids and thelike. The other type is a positron beam method making use of a positronbeam emitted from an electron linear accelerator, as the positronradiation source, and enables an evaluation of pores of thin filmshaving a thickness of several hundred nanometers formed on variousbases. Particularly, in the latter positron beam method, even when ananofiltration membrane is used as a sample to be measured, thefunctional layer of the nanofiltration membrane can be measured only bybringing the membrane to a dry state, and there is no need in particularto perform processing such as separation of the separation functionallayer from the nanofiltration membrane. Therefore, the positron beammethod is more preferred as a method for analysis of the separationfunctional layer of a nanofiltration membrane.

In the positron beam method, the measurement band in the depth directionfrom the sample surface is regulated on the basis of the amount ofenergy of the incident positron beam. As the energy is increased, aproportion that is deeper from the sample surface is included in themeasurement band, but the depth is dependent on the density of thesample. To measure the separation functional layer of a nanofiltrationmembrane, when a positron beam enters usually with an energy of about 1keV, a band of about 50 to 150 nm from the sample surface is measured.In the case of a separation functional layer having a thickness of about150 to 300 nm, particularly the central part in the separationfunctional layer can be selectively measured.

A positron and an electron binds with their mutual coulombic force andgenerate positronium Ps, which is a neutral hydrogen-like atom. Ps haspara-positronium, p-Ps, and ortho-positronium, o-Ps, depending onwhether the spins of the positrons and the electrons are antiparallel orparallel, or the like, and the para-positronium and theortho-positronium are generated at a ratio of 1:3 according to the spinstatistics theorem. Their respective average lifetimes are 125 p for thep-Ps and 140 ps for the o-Ps. However, in a substance in an aggregatedstate, the o-Ps is superposed with an electron that is different fromwhat is bound to itself, and has an increased probability of causing anannihilation called pick-off annihilation. As a result, the averagelifetime of the o-Ps is shortened to a few nanoseconds. The annihilationof the o-Ps in an insulating material is caused by the overlapping of ano-Ps with an electron present on the pore walls in the substance, and asthe pore size is smaller, the annihilation rate is accelerated. That is,the annihilation lifetime of an o-Ps can be correlated to the porediameter in an insulating material.

The annihilation lifetime τ based on the pick-off annihilation of o-Pscan be obtained in an analysis made by dividing a positron annihilationlifetime curve measured by a positron annihilation lifetimespectroscopy, into four components by a non-linear least squaresprogram, POSITRONFIT (the details are described in, for example, P.Kirkegaard, et al., Computer Physic Communications, Vol. 3, p. 240,North Holland Publishing Company (1972)), specifically from the analysisresults for the fourth component.

The average pore radius R in the separation functional layer of thenanofiltration membrane is a value determined from the following formula(1), by using the positron annihilation lifetime τ. The formula (1)represents the relationship in the case of assuming that the o-Ps ispresent in a pore having a radius R in an electron layer having athickness of ΔR, and ΔR is empirically determined to be 0.166 nm (thedetails are described in Nakanishi, et al., Journal of Polymer SciencePart B: Polymer Physics, Vol. 27, p. 1419, John Wiley & Sons,Incorporated (1989)).

$\begin{matrix}{\left\lbrack {{Expression}\mspace{14mu} 1} \right\rbrack\left\lbrack {{Expression}\mspace{14mu} 1} \right\rbrack} & \; \\{\tau^{- 1} = {2\left\lbrack {1 - \frac{R}{R + {\Delta\; R}} + {\frac{1}{2\pi}{\sin\left( \frac{2\pi\; R}{R + {\Delta\; R}} \right)}}} \right\rbrack}} & (1)\end{matrix}$

Upon the expression of the performance of a separation membrane, use ismade of not only the removal rates described above, but also thepermeation performance, which is in a tradeoff relationship with theremoval rates. For example, in a separation membrane having equalremoval rates and high permeation performance, the time required for theseparation operation is shortened, which is preferable. A separationmembrane which exhibits a permeation performance of 0.5 m³/m²d orgreater when a 500 ppm aqueous glucose solution at pH 6.5 at 25° C. ispermeated therethrough at an operation pressure of 0.5 MPa, is used withpreference. A separation membrane exhibiting a permeation performance of0.7 m³/m²d or greater is more preferable because the separationoperation can be performed in a shorter time.

Separation membranes can be carefully selected and connected togetherfor use according to necessity to control the water quality. In regardto the selection and connection of the separation membranes, if at leastone separation membrane that exhibits a glucose removal rate and anisopropyl alcohol removal rate in the ranges described above is used,fermentation inhibitors can be efficiently removed. For example, first,it is acceptable to carry out a treatment roughly by using a separationmembrane having a low removal rate for fermentation inhibitors buthaving high permeation performance, and then to carry out a treatmentfor enhancing water quality by using a separation membrane having lowpermeation performance but having a high removal rate for fermentationinhibitors. Such selection and connection of separation membranes isused with preference in the case where the concentration of themonosaccharide and/or oligosaccharide of a pentose and/or a hexose aswell as the concentration of the fermentation inhibitor are all low,because concentration and removal of the fermentation inhibitor can becarried out simultaneously.

The shape of the separation membrane is not particularly limited as longas the membrane is capable of treating a polysaccharide-based biomass,and can be selected for use from a smooth membrane shape, a hollow fibermembrane shape, a pleated membrane shape, a tubular membrane shape, andthe like. Particularly, a so-called spiral type element, which isproduced by processing a smooth membrane into an envelop shape, androlling the membrane into a whirled shape together with various memberssuch as a net, is used with preference, because the membrane area can beenlarged.

The separation membrane may be disposed from a point where afermentation inhibitor is generated, to a point where the fermentationinhibitor is transported to the steps which are adversely affected bythe fermentation inhibitor, such as saccharification making use of anenzyme, and separation processes, so that the fermentation inhibitor maybe removed to the extent that the fermentation inhibitor does notadversely affect the subsequent processes. Furthermore, to control thewater quality, the method of supplying raw water to the separationmembrane can also be freely designed, such that the recovery rate ismodified, or a part of the raw water is circulated. For example, themethod of supplying may also be modified based on the type of thepolysaccharide-based biomass.

As such, the treatment of a polysaccharide-based biomass with the use ofa separation membrane has a high degree of freedom in design, and thuseven when various polysaccharide-based biomasses are used as startingmaterials, the fermentation inhibitor can be removed to the extent thatfermentation inhibitors do not adversely affect the subsequentprocesses.

Furthermore, to remove a fermentation inhibitor from a solutioncontaining a monosaccharide and/or an oligosaccharide of a pentoseand/or a hexose, by using a separation membrane exhibiting a glucoseremoval rate and an isopropyl alcohol removal rate in the rangesmentioned above, the monosaccharide and/or oligosaccharide of a pentoseand/or a hexose is more concentrated than the fermentation inhibitor,and is recovered to a brine side. That is, when a separation membraneexhibiting a glucose removal rate and an isopropyl alcohol removal ratein the ranges described above is used, a situation may occur whereconcentration of a monosaccharide and/or an oligosaccharide of a pentoseand/or a hexose can be carried out simultaneously while a fermentationinhibitor is removed. Thus, the separation membrane can be particularlysuitably used in a solution having a low concentration of amonosaccharide and/or an oligosaccharide of a pentose and/or a hexose.As a result, a conventional method which requires two steps of a stepfor concentrating a monosaccharide and/or an oligosaccharide of apentose and/or a hexose, and a step for removing a fermentationinhibitor, can be shortened into a single step, or the burden of theconcentration step can be reduced.

Hereinafter, our methods will be described by way of specific Examples,but this disclosure is not intended to be limited by these Examples.

EXAMPLES

The measurements in Examples and Comparative Examples were carried outas follows. Furthermore, separation membranes A to G used in theExamples and Comparative Examples were produced as follows.

In Examples 1 to 8 and Comparative Examples 1 and 2, the following modelaqueous solution was prepared and supplied to various separationmembranes, to evaluate whether a fermentation inhibitor can be removedfrom a monosaccharide and/or an oligosaccharide of a pentose and/or ahexose. That is, glucose and sucrose were used as the monosaccharideand/or oligosaccharide of a pentose and/or a hexose, and furfural,5-hydroxymethylfurfural and vanillin were used as fermentationinhibitors. A model aqueous solution was prepared by dissolving each ofthe substances in water to a concentration of 500 ppm.

In Example 9, glucose was used as the monosaccharide and/oroligosaccharide of a pentose and/or a hexose, and furfural,5-hydroxymethylfurfural and vanillin were used as fermentationinhibitors, so as to investigate the effect of the fermentationinhibitor concentration on the growth rate of a colon bacillus andyeast.

(Isopropyl Alcohol Removal Rate)

An evaluation was made by comparing the isopropyl alcohol concentrationsin the permeation water and the source water, which were obtained when a500 ppm aqueous isopropyl alcohol solution adjusted to pH 6.5 and atemperature of 25° C. was supplied to a separation membrane at anoperation pressure of 0.5 MPa. That is, calculation was performed by theformula: isopropyl alcohol removal rate (%)=100×(1−(isopropyl alcoholconcentration in permeation water/isopropyl alcohol concentration insource water)). The isopropyl alcohol concentration was determined byconventional gas chromatography analysis.

(Glucose Removal Rate)

An evaluation was made by comparing the glucose concentrations in thepermeation water and the source water, which were obtained when a 500ppm aqueous glucose solution adjusted to pH 6.5 and a temperature of 25°C. was supplied to a separation membrane at an operation pressure of 0.5MPa. That is, calculation was performed by the formula: glucose removalrate (%)=100×(1−(glucose concentration in permeation water/glucoseconcentration in source water)). The glucose concentration wasdetermined by using a refractometer (RID-6A, manufactured by ShimadzuCorp.).

(Permeation Performance)

The amount of permeation water (m³) per unit time (d) and unit area (m²)obtained when a 500 ppm aqueous glucose solution adjusted to pH 6.5 at atemperature of 25° C. was supplied to a separation membrane at anoperation pressure of 0.5 MPa, was measured, and the permeationperformance (m³/m²d) was calculated.

(Positron Annihilation Lifetime Spectroscopy According to Positron BeamMethod)

To perform positron annihilation lifetime spectroscopy withoutparticularly processing the separation functional layer of a separationmembrane, the analysis may be made by using a positron beam method asfollows. That is, a measurement sample dried under reduced pressure atroom temperature and cut to a size of 1.5 cm×1.5 cm, was measured withthin film corresponding positron annihilation lifetime measuringapparatus having a positron beam generating apparatus (the details ofthe apparatus are described in, for example, Radiation Physics andChemistry, vol. 58, p. 603, Pergamon Press (2000)), with a beamintensity of 1 keV, in a vacuum at room temperature, at a total countnumber of 5,000,000 by means of a scintillation counter made of bariumdifluoride using a photomultiplier tube. An interpretation is performedwith POSITRONFIT. From the average lifetime τ of the fourth componentobtained by the interpretation, the average pore radius R, average porevolume V, relative intensity I, and amount pores V×I can be analyzed.

(Production of Polysulfone Supporting Film)

The polysulfone supporting film was produced by the following technique.That is, a wet non-woven cloth of a mixed fabric of polyester fibersrespectively having a single yarn fineness of 0.5 and 1.5 decitex, thenon-woven cloth having a size of 30 cm in length and 20 cm in width, anair permeability of 0.7 cm³/cm². second and an average pore diameter of7 μm or less, was fixed onto a glass plate. A solution of polysulfone ata concentration 15 wt % in a dimethylformamide (DMF) solvent (2.5 Poise:20° C.) was cast on the wet non-woven cloth to a total thickness of 200μm, and the assembly was immediately submerged in water. Thus, apolysulfone supporting film was obtained.

(Production of Separation Membrane A)

The polysulfone supporting film was immersed for 2 minutes in an aqueoussolution containing 2.0 wt % of m-phenylenediamine and 2.0 wt % ofε-caprolactam, and then a solution prepared by dissolving trimesic acidchloride in decane to a concentration of 0.1 wt % was applied thereon toa proportion of 160 cm³/m². Then, excess solution was removed, and thusa separation membrane was obtained. The separation membrane thusobtained was treated for 2 minutes at room temperature with an aqueoussolution containing 0.07 wt % of sodium nitrite and 0.1 wt % ofconcentrated sulfuric acid, subsequently was immediately washed withwater, and was stored at room temperature. Thus, a separation membrane Awas obtained.

(Production of Separation Membrane B)

20.0 g of ethanol and 10.8 g of glycerin were added to a beaker, andwhile the mixture was vigorously stirred, 20.0 g oftetra-n-butoxytitanium was added thereto. After 5 minutes, while the gelthus obtained was stirred with a glass rod, 6.0 g of 28% aqueous ammoniawas added thereto. After the gel turned into a cloudy solution form, thegel was further stirred for 2 hours with a stirrer. The cloudy solutionthus obtained was subjected to a centrifuge (2,500 rpm, 3 minutes).Precipitated white solids were made into a cloudy solution again withethanol, and the cloudy solution was subjected to a centrifuge (2,500rpm, 3 minutes). Precipitated white solids were recovered. The whitesolids thus obtained were dried in a vacuum at normal temperature, andwas further dried in a vacuum at 120° C. for 3 hours. Thus, a whitesolid in a powder form was obtained.

The white solid in a powder form thus obtained was prepared into adilute hydrochloric acid solution (whit solid/water/1 N hydrochloricacid=1/5.5/3.5 wt %), and the solution was applied on the polysulfonesupporting film. Liquid droplets at the surface were removed by nitrogenblowing, and then the assembly was dried for one hour with a hot airdryer at 90° C. Thus, a separation membrane B was obtained.

(Production of Separation Membrane C)

The polysulfone supporting film was immersed for 2 minutes in an aqueoussolution containing 2.0 wt % of m-phenylenediamine and 2.0 wt % ofs-caprolactam, and then a solution prepared by dissolving trimesic acidchloride in decane to a concentration of 0.1 wt % was applied thereon toa proportion of 160 cm³/m². Then, excess solution was removed, and thusa separation membrane was obtained. The separation membrane thusobtained was treated for 2 minutes at room temperature with an aqueoussolution containing 7 wt % of sodium nitrite and 0.1 wt % ofconcentrated sulfuric acid, subsequently was immediately washed withwater, and was stored at room temperature. Thus, a separation membrane Cwas obtained.

(Production of Separation Membrane D)

The polysulfone supporting film was immersed for 2 minutes in an aqueoussolution containing 2.0 wt % of m-phenylenediamine and 2.0 wt % ofs-caprolactam, and then a solution prepared by dissolving trimesic acidchloride in decane to a concentration of 0.1 wt % was applied thereon toa proportion of 160 cm³/m². Then, excess solution was removed, and thusa separation membrane was obtained. The separation membrane thusobtained was treated for 60 minutes at room temperature with an aqueoussolution containing 0.07 wt % of sodium nitrite and 0.1 wt % ofconcentrated sulfuric acid, subsequently was immediately washed withwater, and was stored at room temperature. Thus, a separation membrane Dwas obtained.

(Production of Separation Membrane E)

The polysulfone supporting film was immersed for 1 minute in an aqueoussolution containing 2.0 wt % of m-phenylenediamine, and then a solutionprepared by dissolving trimesic acid chloride in decane to aconcentration of 0.1 wt % was applied thereon to a proportion of 160cm³/m². Then, excess solution was removed, and the assembly was immersedin a 0.2 wt % aqueous solution of sodium carbonate for 5 minutes. Theseparation membrane thus obtained was immersed for 2 minutes in anaqueous solution of potassium peroxymonosulfate adjusted to aconcentration of 1.0 wt % and pH 6, subsequently was washed immediatelywith water, and was stored at room temperature. Thus, a separationmembrane E was obtained.

(Production of Separation Membrane F)

The polysulfone supporting film was coated with an aqueous solutioncontaining 1.0 wt % of piperazine, 0.2 wt % of1,3-bis(4-piperidyl)-propane, 0.5 wt % of sodium dodecyl sulfate, and1.0 wt % of trisodium phosphate, and was dried with air at roomtemperature for 2 minutes. Subsequently, a solution prepared bydissolving a mixture of isophthalic acid chloride and trimesic acidchloride (weight ratio 2:1) in decane at 1.0 wt %, was applied thereonto a proportion of 160 cm³/m², and the assembly was heat treated for 5minutes with hot air at 100° C. The assembly was then washed immediatelywith water and was stored at room temperature. Thus, a separationmembrane F was obtained.

(Production of Separation Membrane G)

The polysulfone supporting film was coated with an aqueous solutioncontaining 1.0 wt % of piperazine, 0.2 wt % of1,3-bis(4-piperidyl)-propane, 2.0 wt % of sodium dodecyl sulfate, and1.0 wt % of trisodium phosphate, and was dried with hot air at 80° C.for 30 seconds. Subsequently, a solution prepared by dissolving amixture of isophthalic acid chloride and trimesic acid chloride (weightratio 1:1) in decane at 0.5 wt %, was applied thereon to a proportion of160 cm³/m², and the assembly was heat treated for 5 minutes with hot airat 100° C. The assembly was then washed immediately with water and wasstored at room temperature. Thus, a separation membrane G was obtained.

Example 1

UTC-60 (crosslinked polyamide nanofiltration (NF) membrane manufacturedby Toray Industries, Inc.) was used as a separation membrane to evaluatethe isopropyl alcohol removal rate, glucose removal rate, and permeationperformance. UTC-60 had an isopropyl alcohol removal rate of 35%, aglucose removal rate of 95%, and a permeation performance of 1.1 m³/m²d,and the difference between the glucose removal rate and the isopropylalcohol removal rate was 60%. Furthermore, the average pore radius ofUTC-60 as measured by a positron annihilation lifetime spectroscopy wasfrom 2.5 nm to 3.5 nm.

A model aqueous solution adjusted to a temperature of 25° C. and at pH6.5 was supplied at an operation pressure of 0.5 MPa, and the glucoseconcentrations, sucrose concentrations, furfural concentrations,5-hydroxymethylfurfural concentrations and vanillin concentrations ofthe permeation water and the source water were measured using arefractometer (RID-6A, manufactured by Shimadzu Corp.) or anultraviolet-visible absorptiometer (UV VISIBLE SPECTROPHOTOMETER 2450,manufactured by Shimadzu Corp.), and the respective removal rates weredetermined. The results are summarized in Table 1. As it can be seenfrom Table 1, since UTC-60 had high glucose and sucrose removal rates,and low furfural, 5-hydroxymethylfurfural and vanillin removal rates, itwas found that the membrane was capable of removing fermentationinhibitors from a monosaccharide and/or an oligosaccharide of a pentoseand/or a hexose.

Example 2

The operation was performed in the same manner as in Example 1, exceptthat UTC-20 (crosslinked polyamide nanofiltration (NF) membranemanufactured by Toray Industries, Inc.) was used as a separationmembrane. UTC-20 had an isopropyl alcohol removal rate of 30%, a glucoseremoval rate of 84%, and a permeation performance of 0.8 m³/m²d, and thedifference between the glucose removal rate and the isopropyl alcoholremoval rate was 54%. Furthermore, the average pore radius of UTC-20 asmeasured by a positron annihilation lifetime spectroscopy was from 3.5nm to 4.0 nm.

Furthermore, the results of evaluation performed using the model aqueoussolution, are summarized in Table 1. As it can be seen from Table 1,since UTC-20 had high glucose and sucrose removal rates, and lowfurfural, 5-hydroxymethylfurfural and vanillin removal rates, it wasfound that the membrane was capable of removing fermentation inhibitorsfrom a monosaccharide and/or an oligosaccharide of a pentose and/or ahexose.

Example 3

The operation was performed in the same manner as in Example 1, exceptthat the separation membrane A was used as a separation membrane. Theseparation membrane A had an isopropyl alcohol removal rate of 70%, aglucose removal rate of 99.5%, and a permeation performance of 1.3m³/m²d, and the difference between the glucose removal rate and theisopropyl alcohol removal rate was 29.5%. Furthermore, the average poreradius of the separation membrane A as measured by a positronannihilation lifetime spectroscopy was from 0.8 nm to 1.0 nm.

Furthermore, the results of evaluation performed using the model aqueoussolution, are summarized in Table 1. As it can be seen from Table 1, theseparation membrane A had high glucose and sucrose removal rates, and itwas found that there was almost no outflow of glucose and sucrose intothe permeation side. On the other hand, since the removal rates forfurfural, 5-hydroxymethylfurfural and vanillin were lower compared withthe glucose and sucrose removal rates, it was found that the membranewas capable of removing fermentation inhibitors from a monosaccharideand/or an oligosaccharide of a pentose and/or a hexose.

Example 4

The operation was performed in the same manner as in Example 1, exceptthat the separation membrane C was used as a separation membrane. Theseparation membrane C had an isopropyl alcohol removal rate of 62%, aglucose removal rate of 99%, and a permeation performance of 1.6 m³/m²d,and the difference between the glucose removal rate and the isopropylalcohol removal rate was 37%. Furthermore, the average pore radius ofthe separation membrane A as measured by a positron annihilationlifetime spectroscopy was from 1.0 nm to 1.5 nm.

Furthermore, the results of evaluation performed using the model aqueoussolution, are summarized in Table 1. As it can be seen from Table 1, theseparation membrane A had high glucose and sucrose removal rates, and itwas found that there was almost no outflow of glucose and sucrose intothe permeation side. On the other hand, since the removal rates forfurfural, 5-hydroxymethylfurfural and vanillin were lower compared withthe glucose and sucrose removal rates, it was found that the membranewas capable of removing fermentation inhibitors from a monosaccharideand/or an oligosaccharide of a pentose and/or a hexose.

Example 5

The operation was performed in the same manner as in Example 1, exceptthat the separation membrane D was used as a separation membrane. Theseparation membrane D had an isopropyl alcohol removal rate of 60%, aglucose removal rate of 98.5%, and a permeation performance of 1.7m³/m²d, and the difference between the glucose removal rate and theisopropyl alcohol removal rate was 38.5%. Furthermore, the average poreradius of the separation membrane A as measured by a positronannihilation lifetime spectroscopy was from 1.0 nm to 1.7 nm.

Furthermore, the results of evaluation performed using the model aqueoussolution, are summarized in Table 1. As it can be seen from Table 1, theseparation membrane A had high glucose and sucrose removal rates, and itwas found that there was almost no outflow of glucose and sucrose intothe permeation side. On the other hand, since the removal rates forfurfural, 5-hydroxymethylfurfural and vanillin were lower compared withthe glucose and sucrose removal rates, it was found that the membranewas capable of removing fermentation inhibitors from a monosaccharideand/or an oligosaccharide of a pentose and/or a hexose.

Example 6

The operation was performed in the same manner as in Example 1, exceptthat the separation membrane E was used as a separation membrane. Theseparation membrane E had an isopropyl alcohol removal rate of 75%, aglucose removal rate of 98%, and a permeation performance of 0.9 m³/m²d,and the difference between the glucose removal rate and the isopropylalcohol removal rate was 23%. Furthermore, the average pore radius ofthe separation membrane A as measured by a positron annihilationlifetime spectroscopy was from 0.8 nm to 1.5 nm.

Furthermore, the results of evaluation performed using the model aqueoussolution, are summarized in Table 1. As it can be seen from Table 1, theseparation membrane A had high glucose and sucrose removal rates, and itwas found that there was almost no outflow of glucose and sucrose intothe permeation side. On the other hand, since the removal rates forfurfural, 5-hydroxymethylfurfural and vanillin were lower compared withthe glucose and sucrose removal rates, it was found that the membranewas capable of removing fermentation inhibitors from a monosaccharideand/or an oligosaccharide of a pentose and/or a hexose.

Example 7

The operation was performed in the same manner as in Example 1, exceptthat the separation membrane F was used as a separation membrane. Theseparation membrane F had an isopropyl alcohol removal rate of 32%, aglucose removal rate of 90%, and a permeation performance of 1.5 m³/m²d,and the difference between the glucose removal rate and the isopropylalcohol removal rate was 58%. Furthermore, the average pore radius ofthe separation membrane A as measured by a positron annihilationlifetime spectroscopy was from 2.5 nm to 3.5 nm.

Furthermore, the results of evaluation performed using the model aqueoussolution, are summarized in Table 1. As it can be seen from Table 1, theseparation membrane A had high glucose and sucrose removal rates, and itwas found that there was almost no outflow of glucose and sucrose intothe permeation side. On the other hand, since the removal rates forfurfural, 5-hydroxymethylfurfural and vanillin were lower compared withthe glucose and sucrose removal rates, it was found that the membranewas capable of removing fermentation inhibitors from a monosaccharideand/or an oligosaccharide of a pentose and/or a hexose.

Example 8

The operation was performed in the same manner as in Example 1, exceptthat the separation membrane G was used as a separation membrane. Theseparation membrane G had an isopropyl alcohol removal rate of 36%, aglucose removal rate of 95%, and a permeation performance of 1.3 m³/m²d,and the difference between the glucose removal rate and the isopropylalcohol removal rate was 59%. Furthermore, the average pore radius ofthe separation membrane A as measured by a positron annihilationlifetime spectroscopy was from 2.5 nm to 3.5 nm.

Furthermore, the results of evaluation performed using the model aqueoussolution, are summarized in Table 1. As it can be seen from Table 1, theseparation membrane A had high glucose and sucrose removal rates, and itwas found that there was almost no outflow of glucose and sucrose intothe permeation side. On the other hand, since the removal rates forfurfural, 5-hydroxymethylfurfural and vanillin were lower compared withthe glucose and sucrose removal rates, it was found that the membranewas capable of removing fermentation inhibitors from a monosaccharideand/or an oligosaccharide of a pentose and/or a hexose.

Comparative Example 1

The operation was performed in the same manner as in Example 1, exceptthat UTC-70U (crosslinked polyamide reverse osmosis (RO) membranemanufactured by Toray Industries, Inc.) was used as a separationmembrane. UTC-70U had an isopropyl alcohol removal rate of 96.2%, aglucose removal rate of 99.9%, and a permeation performance of 0.7m³/m²d, and the difference between the glucose removal rate and theisopropyl alcohol removal rate was only 3.7%. Furthermore, the averagepore radius of UTC-70U as measured by a positron annihilation lifetimespectroscopy was from 0.25 nm to 0.35 nm.

Furthermore, the results of evaluation performed using the model aqueoussolution, are summarized in Table 1. As it can be seen from Table 1,UTC-70U had high glucose and sucrose removal rates, but the removalrates for furfural, 5-hydroxymethylfurfural and vanillin were also high.Therefore, it was found that it is difficult for the membrane to removefermentation inhibitors from a monosaccharide and/or an oligosaccharideof a pentose and/or a hexose.

Comparative Example 2

The operation was performed in the same manner as in Example 1, exceptthat the separation membrane B was used as a separation membrane. Theseparation membrane B had an isopropyl alcohol removal rate of 1%, aglucose removal rate of 29%, and a permeation performance of 2.0 m³/m²d,and the difference between the glucose removal rate and the isopropylalcohol removal rate was 28%. Furthermore, probably because the porediameter of the separation membrane B was too large, the average poreradius of the separation membrane B could not be measured by a positronannihilation lifetime spectroscopy.

Furthermore, the results of evaluation performed using the model aqueoussolution, are summarized in Table 1. As it can be seen from Table 1,since the separation membrane B had low glucose and sucrose removalrates, it was found that a monosaccharide and/or an oligosaccharide of apentose and/or a hexose has flowed out.

Example 9

A spiral type element SU-620 (manufactured by Toray Industries, Inc.,membrane area 28 m²) containing the UTC-60 used in Example 1 as aseparation membrane, was purchased, and this spiral type element SU-620was used to treat 100 L of a solution (1) containing 1.0 wt % ofglucose, 1000 ppm of furfural, 1000 ppm of 5-hydroxymethylfurfural and1000 ppm of vanillin at a recovery rate of 60%. As a result, 40 L of asolution (2) containing 2.4 wt % of glucose, 1150 ppm of furfural, 1200ppm of 5-hydroxymethylfurfural and 1150 ppm of vanillin was obtained.Water was added to the solution (2) to adjust the glucose concentrationto 1.0 wt %, and thus a solution (3) containing 480 ppm of furfural, 500ppm of 5-hydroxymethylfurfural and 480 ppm of vanillin was obtained.

The solution (3) was treated again using SU-620 at a recovery rate of60%, and as a result, a solution (4) containing 2.4 wt % of glucose, 550ppm of furfural, 600 ppm of 5-hydroxymethylfurfural and 550 ppm ofvanillin was obtained. Water was added to the solution (4) to adjust theglucose concentration to 1.0 wt %, and thus a solution (5) containing230 ppm of furfural, 250 ppm of 5-hydroxymethylfurfural and 230 ppm ofvanillin was obtained.

The solution (5) was further treated using SU-620 at a recovery rate of60%, and as a result, a solution (6) containing 2.4 wt % of glucose, 290ppm of furfural, 310 ppm of 5-hydroxymethylfurfural and 290 ppm ofvanillin was obtained. Water was added to the solution (6) to adjust theglucose concentration to 1.0 wt %, and thus a solution (7) containing120 ppm of furfural, 130 ppm of 5-hydroxymethylfurfural and 120 ppm ofvanillin was obtained.

A solution (0) which contained 1.0 wt % of glucose only and did notcontain furfural, 5-hydroxymethylfurfural and vanillin was prepared.

The reason for adjusting the glucose concentration of each solution to1.0 wt % was to evaluate the growth rates of colon bacillus and yeastthat will be described below, at an equal glucose concentration.

The measurement of the concentrations of glucose, furfural,5-hydroxymethylfurfural and vanillin was carried out using highperformance liquid chromatography. That is, a liquid chromatographicliquid transport unit (LC-10AD, manufactured by Shimadzu Corp.) wasused, and a commercially available reverse phase column (ODS column) anda commercially available sugar separation column (CAPCELL PAK NH2SG)were used to perform separation. The respective concentrations weremeasured using a refractometer (RID-6A, manufactured by Shimadzu Corp.)or an ultraviolet visible absorptiometer (SPD-10A, manufactured byShimadzu Corp.) as detectors.

The solutions (0), (1), (3) and (7) were used as substrates, and thegrowth rates of colon bacillus and yeast were evaluated. Thus, theeffect of the concentrations of furfural, 5-hydroxymethylfurfural andvanillin on fermentation was investigated.

The growth rates of colon bacillus and yeast were evaluated by thefollowing method.

A colon bacillus (Escherichia coli strain W3110) and yeast(Saccharomyces cerevisiae NBRC2260) were used as the bacteria undertest. The colon bacillus and the yeast were subjected to shaken culture(whole culture) at 30° C. for 24 hours, using LB medium (1% trypton,0.5% yeast extract and 1% sodium chloride) for the colon bacillus andusing YPD medium (2% trypton, 1% yeast extract and 2% glucose) for theyeast. As evaluation media, evaluation media (0), (1), (3) and (7) wereprepared by adding corn sleep liquor to the solutions (0), (1), (3) and(7) to obtain a final concentration of 5%, and adjusting the solutionsto pH 7. To 50 mL each of these evaluation media ((0), (1), (3) and(7)), 3 mL of the culture liquor obtained after whole culture was added,and the mixtures were subjected to shaking culture at 30° C. for 24hours. The growth amounts of the colon bacillus and yeast after 24 hoursof culture were calculated by measuring the absorbance at 600 nm (OD600value). When the OD600 value of the colon bacillus or yeast after 24hours in the evaluation medium (0) was taken as 100, the respectivegrowth rates in the evaluation media (1), (3) and (7) are summarized inTable 2.

Particularly, the evaluation medium (7) containing 120 to 130 ppm offurfural 5-hydroxymethylfurfural and vanillin concentrations, exhibitedgrowth rates of the colon bacillus and yeast that were almost equal tothe growth rates obtainable in the evaluation medium (0) which did notcontain furfural, 5-hydroxymethylfurfural and vanillin, and thus aremarkable effect of removing fermentation inhibitors was observed.

TABLE 1-1 Example 1 Example 2 Example 3 Example 4 Example 5 Type ofseparation membrane UTC-60 UTC-20 Separation Separation Separationmembrane A membrane C membrane D Isopropyl alcohol removal rate (%) 3530 70 62 60 Glucose removal rate (%) 95 84 99.5 99 98.5 Glucose removalrate (%) − Isopropyl alcohol removal rate (%) 60 54 29.5 37 38.5Permeation performance (m²/m²d) 1.1 0.8 1.3 1.6 1.7 Model Glucoseremoval rate (%) 92 80 99 98.5 97 aqueous Sucrose removal rate (%) 99 8899.9 99.9 99 solution Furfural removal rate (%) 9 10 90 83 805-Hydroxymethylfurfural removal rate (%) 13 12 93 89 86 Vanillin removalrate (%) 10 10 90 84 82 Average pore radius based on positronannihilation lifetime 2.5-3.5 3.5-4.0 0.8-1.0 1.0-1.5 1.0-1.7measurement method (nm)

TABLE 1-2 Comparative Comparative Example 6 Example 7 Example 8 Example1 Example 2 Type of separation membrane Separation Separation SeparationUTC-70U Separation membrane membrane membrane membrane E F G B Isopropylalcohol removal rate (%) 75 32 36 96.2  1 Glucose removal rate (%) 98 9095 99.9 29 Glucose removal rate (%) − Isopropyl alcohol removal rate (%)23 58 59 3.7  28 Permeation performance (m²/m²d) 0.9 1.5 1.3 0.7   2Model Glucose removal rate (%) 97 87 89 99.9 28 aqueous Sucrose removalrate (%) 99 95 97 99.9 33 solution Furfural removal rate (%) 86 7 8 99.9 0 5-Hydroxymethylfurfural removal rate (%) 90 8 10 99.9  0 Vanillinremoval rate (%) 90 8 11 99.9  0 Average pore radius based on positronannihilation lifetime 0.8-1.5 2.5-3.5 2.5-3.5 0.25-0.35 Unmeasurablemeasurement method (nm)

TABLE 2 Evaluation medium (1) (3) (7) (0) Solution (1) (3) (7) (0)Glucose concentration (wt %) 1.0 1.0 1.0 1.0 Furfural concentration(ppm) 1000 480 120 0 5-Hydroxymethylfurfural 1000 500 130 0concentration (ppm) Vanillin concentration (ppm) 1000 480 120 0 Growthrate of colon bacillus 5 18 92 100 (—) Growth rate of yeast (—) 23 62 96100Industrial Applicability

The method of producing a compound originating from apolysaccharide-based biomass can be suitably used when saccharides areproduced by using a polysaccharide-based biomass as a starting material,and when the saccharides thus obtained are converted into chemicals viafermentation.

The invention claimed is:
 1. A method of producing a compoundoriginating from a polysaccharide-based biomass comprising: at least oneof a saccharification step that produces a sugar solution containing 1)a monosaccharide and an oligosaccharide or 2) a monosaccharide or 3) anoligosaccharide from a product obtainable by hydrolyzing thepolysaccharide-based biomass; a fermentation step that ferments thesugar solution containing 1) the monosaccharide and oligosaccharide or2) the monosaccharide or 3) the oligosaccharide originating from thepolysaccharide-based biomass; and a treatment step that removes afermentation inhibitor with a nanofiltration membrane comprising atleast one selected from the group consisting of a cross-linkedpiperazine polyamide nanofiltration membrane, a cellulose acetatenanofiltration membrane and a polyamide nanofiltration membrane, havinga glucose removal rate and an isopropyl alcohol removal rate whichsimultaneously satisfy relationships (I) and (II) when a 500 parts permillion (ppm) aqueous glucose solution at pH 6.5 at 25° C. and a 500 ppmaqueous isopropyl alcohol solution at pH 6.5 at 25° C. are respectivelypermeated through the membrane at an operation pressure of 0.5MegaPascals (MPa), 1) prior to the saccharification step and in the stepprior to the fermentation step or 2)prior to the saccharification stepor 3) in the step prior to the fermentation step:Glucose removal rate≧80%  (I)Glucose removal rate−Isopropyl alcohol removal rate≧20%  (II).
 2. Themethod according to claim 1, wherein said nanofiltration membrane is acomposite membrane comprising polyamide as a functional layer on apolysulfone supporting film.
 3. The method according to claim 1, whereinthe treatment step that removes the fermentation inhibitor with thenanofiltration membrane facilitates removal of the fermentationinhibitor and concurrent concentration of any one of cellulose, ahemicellulose, a monosaccharide and an oligosaccharide.
 4. The methodaccording to claim 2, wherein the treatment step that removes thefermentation inhibitor with the nanofiltration membrane facilitatesremoval of the fermentation inhibitor and concurrent concentration ofany one of cellulose, a hemicellulose, a monosaccharide and anoligosaccharide.
 5. The method according to claim 1, further comprisinga treatment step that concentrates the compound with a reverse osmosismembrane performed after the treatment step that removes thefermentation inhibitor and before the fermentation step.
 6. The methodaccording to claim 2, further comprising a treatment step thatconcentrates the compound with a reverse osmosis membrane performedafter the treatment step that removes the fermentation inhibitor andbefore the fermentation step.
 7. The method according to claim 1,wherein the treatment step that removes the fermentation inhibitor iscarried out until content of the fermentation inhibitor in the sugarsolution obtainable immediately before the fermentation step reaches 500ppm or less.
 8. The method according to claim 2, wherein the treatmentstep that removes the fermentation inhibitor is carried out untilcontent of the fermentation inhibitor in the sugar solution obtainableimmediately before the fermentation step reaches 500 ppm or less.
 9. Themethod according to claim 1, wherein the nanofiltration membrane haspores with an average pore radius as measured by a positron annihilationlifetime spectroscopy of 0.8 nm to 4.0 nm.
 10. The method according toclaim 2, wherein the nanofiltration membrane has pores with an averagepore radius as measured by a positron annihilation lifetime spectroscopyof 0.8 nm to 4.0 nm.
 11. The method according to claim 9, whereinaverage pore radius is 2.5 nm to 4.0 nm.
 12. The method according toclaim 10, wherein average pore radius is 2.5 nm to 4.0 nm.